Isolate and identify tumor-related antigens from neoplastic human mammary epithelial cells and develop assays that will be useful in clinical diagnosis, prognosis, and evaluation of therapeutic measures. Determine whether tumor-related antigens from different patients with breast cancer possess common antigenic determinants, and whether these are related to antigenic determinants in neoplastic cells of other organs. Identify structural features that are similar or identical among tumor-related antigens.